• Transactions of the Korean Society for Noise and Vibration Engineering
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• 제22권11호
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• pp.1071-1077
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• 2012

Low frequency noises(up to about 200 Hz) such as booming are mainly caused by particular modes, and in general the solutions may be found based on mode controls where conventional methods such as FEM can be used. However, at higher frequencies between 0.3~1 kHz, as the number of modes rapidly increases, radiation characteristics from structures, performances of damping sheets and sound packages may be more crucial rather than particular modes, and consequently the conventional FEM may be less practical in dealing with this kinds of structure-borne problems. In this context, so-called 'mid-frequency simulation model' based on FE-SEA hybrid method is studied and validated to reduce noise in this frequency region. Energy transmission loss(i.e. air borne noise) is also studied. A dash panel component is chosen for this study, which is an important path that transmits both structure-borne and air borne energies into the cavity. Design modifications including structural modifications, attachment of damping sheets and application of different sound packages are taken into account and the corresponding noise characteristics are experimentally identified. It is found that the dash member behaves as a noise path. The damping sheet and sound packages have similar influences on both sound radiation and transmission loss. The comparison between experiments and simulations shows that this model could be used to predict the tendency of noise improvement.

• Proceedings of the KSR Conference
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.258-264
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• 2007

Floating floors, which are mainly used for reducing interior noise levels of railway vehicle, are known to be superior to single structure in respect to sound transmission loss and vibration reduction performances. The stiffness of isolator is one of the important design variables in floating floors. From modal tests, modal properties of underframe, top floor and isolators are derived. They are used as input parameters for predicting structure-borne noise using AUTOSEA.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.1060-1065
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• 2007

This paper summarizes a design procedure of radiated noise from engine blocks of marine engines. This air-borne noise is one of the significant noise contributors including the aeroacoustic noise due to intake and exhaust and the re-radiation due to structure-borne noise. Excitation forces by engine operations are evaluated taking into account the power generation mechanism from the burning process to the subsequence motion of internal parts; piston, connecting rod, and crank shaft. The acoustic transfer vector method is incorporated to effectively simulate the radiated noise field under the various operation conditions. A contribution analysis for the various excitations to the radiated noise is conducted. It is found that the firing pressure is the main source of the radiated noise, and so the structure of the cylinder can be modified to significantly reduce the radiated noise from the engine block.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.145-151
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• 2008

URN(Underwater Radiated Noise) is one of the important performances of the battle ship related to the stealth. The main source of the URN is the structure-borne noise on the hull. And the pipe vibration transmitted to the hull is the main source of the structure-borne noise when the speed of the ship is lower than CIS(Cavitation Inception Speed). In this paper, the vibration isolator(rubber mount) for the pipe system is described in order to reduce the structure-borne noise transmitted to the hull. The vibrations on the sea-water conveying pipes and their supports are measured in order to know how much vibration occurs on those positions. Based on these test results, the improved design of the rubber mount is suggested by the parametric study and is verified numerically with the pipe and hull model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.268-272
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• 2002

A study to determine the structure-borne noise radiated by a dash panel of a real car is performed by using the finite element method (FEM) and the boundary element method (BEM). The radiation efficiency is used to estimate the structure-borne noise radiated by a dash panel. The curved surfaces of a dash panel change the radiation efficiency. Experimental results of radiation efficiency of a simple rectangular plate and a dash panel show good agreements with the simulation results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.407-410
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• 2007

In the ship-building industry, reciprocating air condensing compressors are usually applied in the HVAC system because of their good performance, efficiency and the convenience. However, the inertia force and pressure fluctuation of the compressor may generate unexpected excessive noise and vibration in the near by cabins. This paper presents a theoretical background and appropriate countermeasures on the reduction of structure-borne noise from the compressors.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.667-672
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• 2007

The source of wayside noise for the train are the aerodynamic noise, wheel/rail noise, and power unit noise. The major source of railway noise is the wheel/rail noise caused by the interaction between the wheels and rails. The Structure borne noise is mainly a low frequency problem. The train noise and vibration nearby the elevated railway make one specific issue. In this paper, the train noise and structure borne noise by train are measured. From the results, we investigated the effect on the sound absorption tunnel for elevated railway.

• Transactions of the Korean Society of Automotive Engineers
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• 제6권1호
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• pp.122-133
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• 1998

This paper presents the static analysis, the modal analysis and the forced vibration analysis on engine structures to find out the structure-borne noise sources by finite element method. The deformation of engine structures under the maximum combu- stion gas force was calculated through the static analysis, and the resonance possibilities were predicted by the modal analysis which ascertains mode shapes and the corresponding frequencies of engine global and its major noise sources in engine surfaces were investigated with the forced vibration analysis by means of finding the transfer mobilities on engine surfaces due to the piston impact and the velocity levels due to the combustion in consideration of oil film stiffness and damping coefficients. Finally, the direction of engine structure-borne noise reduction can be estabilished by the above-mentioned analysis procedure and the reduction effect of cost on proto-type engine build-up is expected.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.942-947
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• 2002

In this study, reduction of airborne and structure-borne noise of naval ship pump is presented. Since piping system arrangement such as valve location, flexible joint, pipe diameter and elbow location, discharge basin affect greatly on the noise measurement, care must be taken to minimize the unnecessary noise from the piping system. It is shown that structure-borne noise of the motor with single resilient mount system exceeds criterion. Therefore, it is concluded that double resilient mount system is inevitable. Two kinds of mount is studied for upper mount; spring and rubber type. Although both mounts show good performance at low frequency including rpm frequency, 63Hz, spring mount is found to be inadequate at high frequency, because spring coil acts as a path for SBN.

• Proceedings of the KSR Conference
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• 한국철도학회 2006년도 추계학술대회 논문집
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• pp.305-309
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• 2006

In this paper vibration reduction characteristics of floating floors used in railway vehicles are studied. Vibration reduction characteristics are compared through a series of tests for elastically-coupled floor and rigidly-coupled floor. It was found that elastically-coupled floor has larger vibration reduction amount than rigidly-coupled floor. Around the fundamental natural frequency, however, elastic floor has poor vibration reduction effect than rigid floor. Measures to reduce structure-borne noise are also discussed based on the test results. Structure-borne noise for running railway vehicles cannot be reduced by an effort to deviate resonance between natural frequency of floors and major exciting forces. Instead, reducing vibration level of top floor and using covers which have low sound radiation coefficient will be effective for reducing structure-borne noise.